NOTE: To my knowledge this was originally posted on a small private forum by a poster who I know only by his screenname Xagyg117 on that site. A long time lurker who doesn't usually put any of his fiction up on public sites. I felt his critique was so cutting it deserved to be more widely spread and got his permission to repost so it was available to the wider internet. As one can see this is basically a no-holds-barred refutation of everything Rawlings says about the literary mirror of her beloved grandfather. But I felt it had to be spread around because at the end of the day judging by acts alone he was the most evil character in the entire series. We can lay at his feet an unending parade of incompetence, hubris, and destruction caused by a disgusting unwillingness to act decisively no matter the provocation or circumstances. Claiming a position of leadership which he used to march those who followed him in circles getting them killed by terrorists while pretending to do something.

There's a lot of villains in the Harry Potter series. They are young and old, male and female, human and otherwise, magical and muggle. They range from indolent and reformable pests to soul-sucking embodiments of death personified. Not all of them set out to be bad. Some are good people who made bad choices; some are power-mad petty bureaucrats. But if you want to pick out the single person who caused the most damage, it's an easy task.
He is, of course, Albus Dumbledore.
You think I'm joking? On the contrary, through a combination of staggering incompetence, dereliction of duty, and wholly unmerited hubris he managed to spend his entire life busily nurturing minor problems into world-ending catastrophes.
Let's start at the beginning. Like most young English wizards, Dumbledore learned of his talents early in life and entered Hogwarts as soon as he came of age. While there he rose to seldom-seen levels of magical skill and along the way befriended another young wizard named Gellert Grindelwald. Grindelwald was a German expat wizard, having been kicked out of Durmstrang (the German equivalent Hogwarts) for being a dangerous nutjob. If you accept the author's word as canonical, the situation is even weirder: Dumbledore was not merely a friend but actually in love with Grindelwald. The books themselves contain no real indication that Dumbledore batted for the other team, nor does the author give any indication that Grindelwald returned the interest. But however you slice it, they were certainly very close. Lie down with dogs and get up with fleas, and soon enough Grindelwald had Dumbledore solidly radicalized. The two of them plotted to take over the world and rule the muggles for their own good. Dumbledore's younger brother Aberforth had more sense and confronted the two over their plans. Their other sister, the brain-damaged and disabled Ariana, was also there. It would have made a great Jerry Springer episode, what with the gay/racist/disability trifecta. Well, except being wizards they had considerable magical firepower at their disposal and Ariana was killed in the ensuing fight. Good job, Dumbledore!
All that was tragic enough, but things were just getting warmed up. Grindlewald went off and started a massive wizarding war. Dumbledore dithered ineffectually for several years as his former friend / gay lover wrecked Europe. Apparently he didn't want to be reminded that he was at least partially responsible for the death of his sister. Presumably he didn't worry too much about also being at least partially responsible for the FREAKING HOLOCAUST. Because let's be honest about Grindelwald: evil German, interested in a master race ruling the rest of humanity, beaten in 1945, tried and imprisoned in Nurmengard (hmm)... he was either Hitler or the magical power behind the Fuhrer. We do know that the real Hitler was pretty darn interested in the occult, after all.
So Dumbledore finally got out of his funk and defeated Grindelwald in battle. He then retired to the countryside where he could live out his life in peace. Ok, well, the first sentence is true. Actually he went off to become the headmaster of Hogwarts (the British boarding school jokes write themselves) and shape the minds of tomorrow. Because he's clearly such an excellent judge of character.
About this time there's a young half-wizard fellow named Tom Riddle. An orphan from a horribly difficult background, he displays sociopathic tendencies, a serious red-flag magical ability to talk to snakes, and considerable but largely unexplored latent skill in magic. Dumbledore is nothing if not consistent at being a reliably dangerous fool, and so of course he immediately sends him to the one place were he can learn the most powerful abilities on the planet, and furthermore allows a talking hat to place him in Slytherin the psychopath factory. (Why no one shut down Slytherin is beyond me. The best that can be said is that while every dangerous lunatic wizard was a Slytherin, not all Slytherins were dangerous lunatic wizards. Still, they pretty much to a man abandon the good guys in the climactic good/evil battle at the end of the last book. It would've saved everyone a lot of pain if the whole house had been shut down. So obviously Dumbledore didn't.)
As you could guess from Dumbledore's success at working alongside and/or fornicating with wizard Hitler, Tom Riddle turned out pretty much how you'd expect. He declared himself Lord Voldemort, started a magic army of overtly Klan-style terrorist wizards, killed a bunch of people, and rather successfully began taking over. Dumbledore leaped into action and organized the Order of Rank Incompetence. Excuse me, I mean the Order of the Phoenix. So far as I can tell their successes were minimal to nonexistent, consisting largely of a single unsolicited defection. Under the enervated leadership of Dumbledore, a massive fraction of their membership was brutally slaughtered, the parents of the infant Neville Longbottom were tortured to insanity, and James and Lilly Potter were murdered while protecting their infant child Harry Potter. Thanks to some staggering luck that Dumbledore never planned or anticipated, Voldemort failed to kill Harry and was in fact reduced to impotent ghostliness.
Dumbledore, realizing that he was obviously as bad as humanly possible at working with young wizards, retired. Excuse me, that's what he'd have done if he had any decency. He didn't, so he stayed on at Hogwarts.
Harry Potter grew up and matriculated at Hogwarts. Long story short, Dumbledore spends most of the first five books failing to prevent the repeated infestation of Hogwarts by villains of various stripes, failing to do even slight due diligence on the applicants for the Defense Against the Dark Arts class, and failing to prevent the subsequent and repeated near-deaths of Harry and other students. In some cases like the poor unfortunate Cedric Diggory, it's actual death. There's little more Dumbledore likes better than repeating past failures, so he reforms the Order of the Phoenix. It fails to accomplish anything. Well, not other than getting Sirius Black killed horrifyingly right in front of Harry. Good thing he wasn't one of Harry's few real adult friends and father figures - oh wait, he was. And though we don't know it until book 7, Dumbledore figures out at some point that Harry and Voldemort's fates are linked. Not to put too fine a point of it, at that point he's pretty much trying to get Harry killed. His plans are cut short in book 6 by his own death.
Wanna know what kills him? I don't know if you watched Lord of the Rings, but it's pretty much Magic 101 that you DO NOT TOUCH EVIL RINGS OF POWER. Dumbledore found one, and like a retarded puppy licking a electrical outlet, he tried to use it. He survives his injuries for another year, which he spends failing to clue poor Harry in on what's going on. Finally he dies in front of Harry in the most traumatizing way possible.
Harry wins, of course. He gets killed first, but he comes back to life and kills Voldemort for good. Everyone celebrates the memory of Dumbledore because the narrative requires it. Whatever, Dumbledore you old bat. When Snape waxes you I'll be cheering in the theater.